hmm there is nothing new in the article on cactiguide that hasn't already been said/mentioned here ... The high pH of the commercial "distilled" water is a case for discussion ... I bet you anything that it is "demineralized" water and not "distilled". (Worst case the guys his pH meter is badly calibrated) If the demineralizing resins are not equally well generated then they will not perform their job and an alkaline or acid "residue" will "color" the final pH. Trust me, we've made and used tons of distilled and doubly distilled water in molecular biology and the "fresh" product is pH neutral. Upon standing it dissolves CO2 from the air and becomes acidic. There is a nice calculation on one of the US Uni sites that calculates the pH of CO2 saturated water at normal atm pressure and temp.BTW The assumption of the writer that tap water contains CaclciumBIcarbonate is wrong. Water would be undrinkable if it were as it dissolves 166grams per liter. Water hardness causing "alkalinity" is calcium carbonate which for classic hard water is about 100 MILLIgram per liter .. .. and a good pH meter is cheap ? not in my books, at least not if it must give a reliable pH reading.

I was thinking on those questioning the neccesity of watering always with acidified water (versus only watering once in a while to wash up the bicarbonates). I guess this depends on the degree of alkalinity of your water and your mix. Also, it is highlighted the lack of knowledge about long-term effects of using vinegar or other acids. Someone also suggested that there is no sound scientific evidente about ammonium sulphate being better that any other form of nitrogen or a combination of different nitrogen foms. Cheers

The larger problem is salts build-up. Many combinations of fertilizers, soils salts and CO2 result in almost insoluble carbonates. They will never dissolve in the mild acidification as needed in a soil. But there will probably never be any research on this because everyone will probably transplant before the problems occur. (although I've kept cacti for many years, even decades in the same mineral soil) For me, I prefer "mineral" acids (phosphoric) over acetic because I've had bad experiences with acetic due to its organic nature. The caveat with mineral acids is that they are strong acids and as such it is very difficult to adjust the pH of their solutions unless you use buffering which adds additional salts to the mix. But one cannot mess around with unlimited EC values in the soil.Ammonium sulphate seems a product of choice based on its use as a fertilizer in agriculture but I think that UK growers also used Aluminium sulphate which made me wonder about the toxicity but they claimed that it was not a problem .. I doubt that.